Need help getting over my fear/disorder?

Im 19 5'1 male teen, naturally people like me should eat around 2000 calories but Im afraid to go past 800, I used to be 211 pounds than I took control of my life and got my weight done to were its considered healthy 127 128 around those lines, i may be pushing my body into starvation mode but Im still afraid of eating 1000 calories, i don't eat junk food or fast food, i mostly eat whole wheat, greens and fruit. Is this fear part of a disorder, any ideas